Various processes for forming images which comprise polymerizing ethylenically unsaturated compounds by the action of light to form a polymeric compound (polymer) have been proposed. Further, it has been proposed to use silver halide as a catalyst to directly cause photopolymerization as described in British Pat. No. 866,631 and S. Levinos et al., Photographic Science & Engineering, Vol. 6, pages 222-226 (1962). In such cases, it has been believed that the product formed by photolysis of silver halide functions directly as a catalyst for polymerization, and a sensitivity as high as that of the case wherein silver halide particles are reduced by conventional development cannot be obtained.
It has also been proposed to use a process which comprises developing exposed silver halide emulsion particles with a conventional developing solution and polymerizing ethylenically unsaturated compounds by utilizing the formed silver images or unreacted silver halide as a catalyst to imagewise form polymers, as described in Belgian Pat. No. 642,477. This process has a problem in that the development operation and the polymerization operation should be carried out separately.
In a process which comprises developing exposed silver halide in the presence of an ethylenically unsaturated compound using a reducing compound to cause polymerization of the ethylenically unsaturated compounds by the action of an oxidation product or an intermediate product formed in the developing process, it has been proposed to carry out the reaction using a so-called benzenoid compound having two or more hydroxyl groups, amino groups, or amino groups substituted by alkyl or aryl groups, on the ortho- or para-positions of the benzene ring as the reducing agent, as described in U.S. Pat. No. 3,019,104 and G. Oster, Nature, Vol. 180, page 1275 (1957). However, in an example of the reaction by such a benzenoid compound, an increase of the optical density of the silver image is observed, but an increase of the viscosity is not observed. Also, the generation of heat of reaction and the separation of formed polymeric molecules are not observed. So, in this study, the evidence of forming polymeric molecules is not confirmed.
Furthermore, it has been reported by other researchers that they did not succeed in supplementary examinations; e.g., see S. Levinos and F. W. H. Mueller, Photographic Science & Engineering, Vol. 6, page 222 (1962).
It has also been proposed to polymerize ethylenically unsaturated compounds in the presence of exposed silver halide using resorcinol, naphthol, pyrazolone or hydrazine compounds as the polymerization initiator, as described in Japanese Patent Publication No. 6581/71, and U.S. Pat. Nos. 3,697,275, 3,782,944, 3,756,818, 3,767,400, 3,782,943, 3,697,273, 3,707,379, 3,687,667, 3,874,947, 3,756,820, 3,790,378 and 3,746,542. Although a polymer of the ethylenically unsaturated compounds is formed in such cases, the sensitivity thereof is not generally satisfactory.
Further, a process using hydroquinone, etc., as the polymerization initiator, wherein the polymerization reaction is caused on the part where silver halide is not reduced, namely, the unexposed area, to form polymeric images that are negative with respect to the exposed silver halide image has been disclosed in U.S. Pat. No. 4,287,290. However, such a process is not satisfactory from the viewpoint of sensitivity.